Well, you can get about 1000 members. But, if you advertise your site as a Click link. You may do this on PTC too. But, this traffic is not legal as per AdSense. So, you may not be permitted to have this type of traffic through AdSense. However, its waste of time and money coz people will only try to wait until the timer ends. So, Google is good for traffic. Try to do as much as SEO as possible.